A 32-year-old woman who is 14 weeks pregnant (gravida 1, para 0) presents with a 6-week history of exertional palpitations and fatigue. She reports severe palpitations that worsen with activity and are associated with lightheadedness and fatigue. She experiences significant palpitations on standing after lying down for a while. The palpitations improve with lying flat. Her symptoms have significantly limited her level of activity. Her pregnancy has otherwise been uneventful except for nausea and vomiting in the first few weeks. She has hypermobile Ehlers-Danlos syndrome (hEDS) and migraine headaches. She reports no smoking history or alcohol use. She drinks approximately 1.78 L (60 oz) of nonalcoholic fluid daily.
Her vital signs include resting heart rate (HR) 92 bpm taken in a supine position and 136 bpm after 8 min of standing. Respiratory rate is 16 breaths/min, and blood pressure (BP) is 112/72 mm Hg in a supine position and 100/68 mm Hg after standing for 8 min. Physical examination reveals no abnormalities. S1 and S2 are normal; no other heart sounds are heard. There are no murmurs, rubs, or gallops.
Laboratory study results, including complete blood count (CBC) values, electrolyte panel values, and thyroid-stimulating hormone level, are within the reference range. Electrocardiogram (ECG) findings are unremarkable.
The correct answer is: C. Postural orthostatic tachycardia syndrome (POTS).
To maintain the metabolic demands of the expectant mother and fetus and to ensure adequate uteroplacental circulation, there is a decrease in peripheral vascular resistance (which peaks in the second trimester) with an attendant increase in resting HR during pregnancy. This HR increase is usually between 10 and 20 bpm above prepregnancy baseline HR.1 Although there is no absolute cutoff for the upper limit of normal HR in pregnancy, most pregnant patients generally have HRs <120 bpm. HR >120 bpm in a pregnant patient is often abnormal.
In inappropriate sinus tachycardia syndrome, both resting and upright HRs are elevated, as opposed to POTS, in which the resting/supine HR is normal and only the upright (occasionally sitting) HR is significantly elevated.
Pregnancy is associated with an approximate 45% increase in plasma volume, which causes a slight drop in prepregnancy hematocrit levels.1 This change is physiological and does not cause tachycardia. Although anemia could cause tachycardia, this often occurs both at rest and with exertion. Moreover, anemia would be less likely in this patient with CBC values within the reference ranges.
POTS is a syndrome of orthostatic intolerance characterized predominantly by upright tachycardia in the absence of orthostatic hypotension (OH). POTS is the most common form of orthostatic intolerance in young patients and is predominantly common in premenopausal persons of childbearing age. Approximately 0.2-1% of the US population has POTS, and this number has increased significantly after the coronavirus disease 2019 pandemic.2
The diagnosis of POTS requires the following criteria2,3:
- Symptoms of orthostatic intolerance, which include palpitation, lightheadedness, difficulty concentrating, headache, blurry vision, or syncope when standing upright
- Presence of an increased HR of ≥30 bpm (or ≥40 bpm in teenagers) occurring within 10 min of assuming an upright position
- The absence of OH (i.e., <20/10 mm Hg change in BP from supine to standing)
- Exclusion of other conditions that could sufficiently explain the symptoms.
The pathophysiological mechanism of POTS is heterogeneous.4 Possible etiopathology mechanisms include:
- Autoimmunity
- Peripheral sympathetic denervation
- Persistent low plasma volume, which is possibly mediated by inappropriately low plasma renin and aldosterone levels
- Inappropriate release of histamine and other mast cell mediators
- Impaired norepinephrine clearance leading to sympathetic hyperactivity.
POTS symptoms have been reported to begin after conditions such as viral infections, surgery, concussion, pain, and pregnancy.
Patients with POTS who become pregnant are likely to report worsening symptoms during the first and third trimesters and improvement during the second trimester. This worsening is probably due to the increasing maternal blood volume, which peaks during the second trimester. Patients with POTS who become pregnant often have uneventful pregnancy courses. Pregnancy-associated complications occurring in patients with POTS are most likely to result from the comorbidities associated with POTS, such as migraine, hEDS, or autoimmune conditions. Because of the comorbidities often associated with POTS, pregnancy care and delivery would often require a multidisciplinary team, including a cardiologist, maternal and fetal medicine specialist, and anesthesiologist.
In evaluating POTS during pregnancy, a thorough history, physical examination, laboratory studies, and ECG should be performed to identify mimics, causes of autonomic dysfunction, and comorbidities. Laboratory studies should include a minimum of a CBC, electrolyte panel, thyroid function test, and ECG. A 10-min standing test should be performed. Although a tilt table test could aid in diagnosis, this is rarely recommended in the setting of pregnancy.
Most symptoms of POTS during pregnancy can be managed conservatively. First, patient education is critical, as managing expectations can relieve the psychological impact associated with POTS in pregnancy. Other recommendations include ensuring adequate hydration with a goal fluid intake of 2-3 L (68-101 oz) daily, waist-high compression stockings, and increasing consumption of salty foods with daily sodium intake up to 7 g. When conservative approaches do not alleviate symptoms, therapeutic agents such as beta-blockers, midodrine, fludrocortisone, and ivabradine can be safely used in the setting of pregnancy.4,5
Labor may be challenging in patients with POTS because of profound tachycardia from pain and volume depletion. Adequate pain control and hydration should be considered to limit tachycardia. Patients with POTS and hEDS may develop significant hypotension from anesthesia and are at an increased risk of prelabor spontaneous rupture of membrane, precipitous labor, excessive bleeding, and impaired wound healing.5 Patients with hEDS may also respond poorly to lidocaine. Anesthesia and delivery should be planned and coordinated with a multidisciplinary team before labor starts.
POTS is not a contraindication to pregnancy. Most patients with POTS who become pregnant have uneventful pregnancies, but a multidisciplinary team may be needed to care for them.
References
- Morton A. Physiological changes and cardiovascular investigations in pregnancy. Heart Lung Circ 2021;30:e6-e15.
- Bourne KM, Nerenberg KA, Stiles LE, et al. Symptoms of postural orthostatic tachycardia syndrome in pregnancy: a cross-sectional, community-based survey. BJOG 2023;130:1120-27.
- Vernino S, Bourne KM, Stiles LE, et al. Postural orthostatic tachycardia syndrome (POTS): state of the science and clinical care from a 2019 National Institutes of Health expert consensus meeting - part 1. Auton Neurosci 2021;235:[ePub ahead of print].
- Bryarly M, Phillips L, Fu Q, Vernino S, Levine BD. Postural orthostatic tachycardia syndrome: JACC focus seminar. J Am Coll Cardiol 2019;73:1207-28.
- Morgan K, Smith A, Blitshteyn S. POTS and pregnancy: a review of literature and recommendations for evaluation and treatment. Int J Womens Health 2022;14:1831-47.